In percussion drilling machines, it is known that the tool holder comprises at least one ball or cylinder type locking part able to move in a substantially radial direction, which limits the axial mobility of the rod or drill bit, by penetrating the cavities of the latter, the cavities being closed upon both sides in the axial direction thereof.
In certain ones of these drilling machines as described, for example, in the patent FR-1 588 841 (HILTI), these balls or cylinders ensure, not only slidable locking, but also rotary locking by adopting the role of a carrier.
In other drilling machines as described in the patent FR-A-76 34 195 (BOSCH), the tool holder, in addition to the locking part(s), comprises at least one rotary carrier in the form of a key, and often two keys diametrically opposed with respect to each other.
So as to enable a drill bit to be used in the various types of commercial drilling machines, it has already been proposed to provide upon the drill bit rod firstly two diametrically opposed driving grooves and secondly, a locking groove and an opposing parallel axis driving groove located within the same diametrical plane with an opening towards the rear section thereof which is amply larger than the section of the locking groove.
A drill bit fitted out as above can also be properly fitted into both tool holders of the type described in the patent FR 1 588 841 (HILTI) and into the types of tool holders described in the patent FR 76 34 195 (BOSCH), namely with one or two locking balls or one or two driving keys. However, in 50% of the cases, this drill bit may not be retained within tool holders with one locking ball, as the ball is then present within the driving groove which is fully open towards the rear.